Conventionally, radar antennas each including an antenna unit and a housing unit has been known. The antenna unit radiates outside radio waves. The housing unit is built therein with a motor for rotating the antenna unit, a coaxial cable for supplying radio waves to the antenna unit, etc.
Moreover, various kinds of antenna units have conventionally been known, such as, an antenna unit having a shape in which the cross-section of an opening part thereof gradually spreads toward outside (horn shape, trumpet shape). In supporting the horn-shaped antenna unit, it has been known that even if a metal is disposed right beneath or behind the horn part, it does not give any influence on a beam formation. Therefore, conventionally, in order to stably support the horn-shaped antenna unit, the antenna unit is generally substantially directly attached to the housing unit (with an attaching plate interposing therebetween).
Moreover, JP1991-042723A discloses an antenna unit having dielectric bodies. The antenna unit includes a dielectric body waveguide mechanism comprised of two dielectric body flat plates opposing to each other.
However, with the antenna unit having the dielectric bodies as disclosed in JP1991-042723A, when a metal is disposed near the antenna unit, a beam cannot be formed appropriately. Therefore, the antenna unit having the dielectric bodies is preferred not to be disposed near the housing body, different from the conventional horn-shaped antenna unit.
In this regard, JP1991-042723A only discloses the configuration having the shape of the antenna unit with the dielectric bodies, and the details in supporting the antenna unit are not disclosed. For this reason, an appropriate configuration for supporting an antenna unit having dielectric bodies has been desired.
Note that, in JP1991-042723A, the dielectric body flat plates are disclosed to be made of FRP. Here, only the configuration of using FRP to the dielectric body waveguide mechanism of the antenna unit is disclosed and the use of FRP to other members is not disclosed.